Project Summary/Abstract The aim of this proposal is to identify and characterize novel long noncoding RNAs (lncRNAs) that function in monocyte to macrophage differentiation. Macrophages are critical effector cells of the innate immune system where they function to control infection and maintain tissue homeostasis. Macrophages are implicated in the pathogenesis of a number of diseases including rheumatoid arthritis and cancer. A critical process for macrophage function involves their differentiation from monocytes present in the peripheral blood. This is a tightly regulated procedure and here we aim to characterize the role that lncRNA play in controlling this process. We will carry out a systematic unbiased screen using Cas9/CRISPRi technology to identify lncRNAs that function to control monocyte to macrophage differentiation. This will allow for rapid meaningful data to be obtained in a highly efficient manner. In our preliminary RNA-sequencing data we have identified hundreds of lncRNA that display differential expression patterns between monocytes and macrophages. We have begun to establish our mechanistic analysis pipeline by investigating the functions of one lncRNA named GAPLINC, which we have found to be induced over 1000 fold during the differentiation process. Here we will employ a suite of in vitro mechanistic techniques to determine how GAPLINC functions to control macrophage differentiation. This project will establish a foundation for future studies to determine the regulatory importance of lncRNAs in innate immune cell development and inflammatory diseases.